Power plants are thirsty.

Take the average amount of water flowing over Niagara Falls in a minute. Now triple it. That’s almost how much water power plants in the United States take in for cooling each minute, on average.

In 2005, the nation’s thermoelectric power plants—which boil water to create steam, which in turn drives turbines to produce electricity—withdrew as much water as farms did, and more than four times as much as all U.S. residences.

It requires more water, on average, to generate the electricity that lights our rooms, powers our computers and TVs, and runs our household appliances, than the total amount of water we use in our homes for everyday tasks—washing dishes and clothes, showering, flushing toilets, and watering lawns and gardens.

Power plants across the country contribute to water stress.

This tremendous volume of water has to come from somewhere. Across the country, water demand from power plants is combining with pressure from growing populations and other needs, and is straining our water resources—especially during droughts and heat waves.

For example, the 2011 drought in Texas created tension among farmers, cities, and power plants across the state. At least one plant had to cut its output, and some plants had to pipe in water from new sources.

The state power authority warned that several thousand megawatts of electrical capacity might go offline if the drought continued to persist.

In this report, we examine both the withdrawal and consumption of freshwater.

Withdrawal is the total amount of water a power plant takes in from a source such as a river, lake, or aquifer, some of which is returned. Withdrawal is important for several reasons: water intake systems can trap fish and other aquatic wildlife; water withdrawn for cooling but not consumed returns to the environment at a higher temperature, potentially harming fish and other wildlife; and when power plants tap groundwater for cooling, they can deplete aquifers critical for meeting many different needs. Power plants that use once-through cooling technology tend to have high rates of withdrawal.

Consumption is the amount of water lost to evaporation during the cooling process. Consumption is important because it, too, reduces the amount of water available for other uses, including sustaining ecosystems. Plants that use recirculating cooling technology tend to have lower rates of water withdrawal, but consume much of that water through evaporation.

Technology choices matter.

In the short run, our choices for what kind of power plants we build can contribute to freshwater supply stress—by committing an imbalanced share of the available water to power plant use—and can affect water quality, by increasing water temperatures to levels that harm local ecosystems, for example.

Over a longer time frame, those choices can fuel climate change, which in turn affects water quantity—through drought and other extreme weather events—and quality, by raising the temperature of lakes, streams, and rivers.

Population growth and rising demand for water also promise to worsen water stress in many regions of the country already under stress from power plant and other uses.

The power plant portfolios of U.S. companies have widely varying water-use and carbon profiles. Utilities with lower-water plants place less stress on local water sources. Utilities with carbon intensive power plants contribute to long-term water stress by exacerbating climate change.

Data gaps and inaccuracies underestimate water stress.

Collisions and near-misses between energy and water needs point to the importance of accurate, up-to-date information on power plant water demand.

Our analysis, however, reveals a number of gaps and apparent inaccuracies in federal data reported for 2008. As a result, analyses based on that information would have overlooked regions facing water stress

Averting energy-water collisions requires that power plant operators regularly report accurate information on their water use to the U.S. Energy Information Administration (EIA) and state agencies. The EIA has been working to improve such reporting, to better meet the needs of public- and private-sector decision makers. The agency may therefore remedy many of the problems we identified with the 2008 data shortly.

However, providing better information is only the first critical step. Decision makers must then put that information—coupled with sound analyses of water stress—to work in curbing electricity’s thirst, especially in water-stressed regions. Our analysis provides a strong initial basis for making water-smart energy choices.

Power plants are designed to last for decades, and much of our existing infrastructure will continue operating for years. As such, our nation’s precious freshwater resources will face ever more stress. The typically high cost of retrofitting power plants means that decisions on the water impact of today’s plants should consider the risks they pose to freshwater resources and energy reliability throughout their expected lifetime.

Decisions made today about which power plants to build, which to retire, and which energy or cooling technologies to deploy and develop matter.

Understanding how these choices affect water use and water stress will help ensure that the dependence of power plants on water does not compromise that resource, the plants themselves, or the energy we rely on them to provide.